• Clean Technology
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• v.29 no.4
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• pp.305-312
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• 2023

Due to the strengthening of environmental requirements, aging denitrification facilities need to improve their performance. The present study aims to suggest the possibility of improving performance using computational analysis techniques. This involved modifying both the geometric design and the operating conditions, including the flow path shape of the equipment such as the inlet guide vane and the curved diffusing part, and the flow control of the ammonia injection nozzle. The conditions presented in this study were compared with existing operating conditions in terms of the flow uniformity, the NH₃/NO molar ratio of the mixed gas flowing into the catalyst layer, and the total pressure drop of the facility. The flow field applied in the computational analysis ranged from the outlet of the economizer in the combustion furnace to the inlet of the air preheater, the full domain of the denitrification facility. The performances were derived by solving the flow fields using ANSYS-Fluent and the injection amount of ammonia was adjusted for each nozzle using Design Xplorer. Compared to the denitrification performances of the equipment currently in operation, the conditions proposed in this study showed an improvement in the flow uniformity and NH₃/NO composition ratio by 45.1% and 8.7%, respectively, but the total pressure drop increased by 1.24%.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.494-500
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• 2003

The effects of $Al_2$O$_3$ addition upon the sintering range of clay-EAF dust (the specified wastes produced from steel making process) system body which would be used as a constructing bricks were investigated. The slope of apparent density to sintering temperature decreased for Clay-dust body containing 5~15 wt% A1203 sintered at 1200-125$0^{\circ}C$, and the absorption(%) of specimen sintered above 125$0^{\circ}C$ decreased due to the formation of open pores produced by pore bloating. For the specimen without any $Al_2$O$_3$ addition sintered at 1275$^{\circ}C$, the major phase was cristobalite, the small amount of mullite (3Al$_2$O$_3$ 2SiO$_2$) formed and the hematite (Fe$_2$O$_3$) remained. In the Clay-dust system body containing $Al_2$O$_3$ 15 wt%, however, the cristobalite disappeared and the major phase was mullite. Also the part of $Al_2$O$_3$ reacted with hematite to form hercynite (FeAl$_2$O$_4$). From the these results, addition of $Al_2$O$_3$ to Clay-dust system body enlarges a sintering range; decreasing an apparent density and absorption slop to sintering temperature owing to consumption of liquid phase SiO$_2$ at higher temperature and gas-forming component Fe$_2$O$_3$ at reduced atmosphere which would decrease an amount of liquid formed and increase the viscosity of the liquid produced during the sintering process.

• Journal of the Korean Vacuum Society
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• v.22 no.5
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• pp.238-244
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• 2013

Doping process using laser is an important process in fabrication of solar cell for heat treatment. However, the process of using the furnace is difficult to form a selective emitter doping region. The case of using a selective emitter laser doping is required an expensive laser equipment and induce the wafer's structure damage due to high temperature. This study, we fabricated a new costly plasma source. Through this, we research the selective emitter doping. We fabricated that the atmospheric pressure plasma jet injected Ar gas is inputted a low frequency (a few tens kHz). We used shallow doping wafers existing PSG (Phosphorus Silicate Glass) on the shallow doping CZ P-type wafer. Atmospheric plasma treatment time was 15 s and 30 s, and current for making the plasma is 40 mA and 70 mA. We investigated a doping profile by using SIMS (Secondary Ion Mass Spectroscopy) and we grasp the sheet resistance of electrical character by using doping profile. As result of experiment, prolonged doping process time and highly plasma current occur a deeper doping depth, moreover improve sheet resistance. We grasped the wafer's surface damage after atmospheric pressure plasma doping by using SEM (Scanning Electron Microscopy). We check that wafer's surface is not changed after plasma doping and atmospheric pressure doping width is broaden by increase of plasma treatment time and current.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.291-298
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• 2001

Seawater, sediment and biota in the Kwangyang Bay were analyzed by gas chromatography/quartz furnace atomic absorption spectroscopy (GC-QFAAS) to investigate concentrations and distribution pattern of butyltin compounds (TBT, DBT, MBT) during February, April and July, 1996, Marine biota analyzed were Tapes japcnicus and Crassostrea gigas. The concentrations of tributyltin (TBT) in seawater were in the range of ND-15.7 ng/L for the surface and ND-68.5 ng/L for the bottom. The highest concentration of TBT in seawater was detected in April for the both, surface and bottom water. The maximum value of $TBT_{(bottom)}/TBT_{(surface)}$, 3.6 in April showed the increased input of TBT from the surface water in April compared to February (2.1) and July (0.9). The concentrations of TBT in the sediment were in the range of ND-8.5 ng/g dry wt. The highest concentration of TBT in the sediment was measured in July, This result seems to attributed to the removal of TBT from water column via sorption onto particulate matters to the relatively undisturbed underlying sediment and increased input of TBT by increased fluxes of detritus of marine plankton after spring bloom, in July. The mean values of partitioning coefficient ($K_d$) of TBT between seawater and sediment were $3.0\times10^3$(February), $7.4\times10^3$(April) and $9.4\times10^3$(July). The concentrations of TBT in biosamples were in the range of ND-93.30 ng/g dru wt. (T. japonicus) and ND-138.53 ng/g dry wt. (C. gigas). The seasonal variation of TBT contents in biota was remarkable. The $K_d$ (biological concentration factor) was $7-41\times10^3$ for T. japonicus. and $5-34\times10^3$ for C. gigas. The measured TBT concentrations in seawater in the study area was sufficient to cause the imposex of shellfish and to retard the growth of aquatic organisms including oyster upon chronic exposure.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.388-395
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• 2016

This paper explores the photocatalytic sensitivity of cement mortar incorporated with recycled $TiO_2$ from waste water sludge. Basically, $TiO_2$ cluster sank down slowly to the bottom of cement mortar specimen before setting and hardening process. This leads the mismatch of $TiO_2$ concentration on the top and the bottom faces of a specimen. This poorly dispersed $TiO_2$-cement mortar naturally exhibits poor NOx removal efficiency especially on the top of cementitious structure. In architectural engineering application such as building or housing structures, one can simply filp over from the bottom so that more $TiO_2$ concentrated surface can be placed outward into the air. However, in highway pavement case, this could not be applicable due to in-situ installation of concrete pavement. Hence, the dispersion of $TiO_2$ cluster inside the cementitous material is getting important issue onto road construction application. To elaborate this issue, according to our results, silica fume, high-ranged water reducer, viscosity agent, blast furnace slag were not enhanced much of dispersion characteristics of $TiO_2$ cluster. The combination of foaming agent and accelerator of hardening with viscosity agent and small grain size of fine aggregate may help the dispersion of $TiO_2$ inside cementitious materials. Even though the enhanced dispersion were applied to the specimen, NOx removal efficiency doest not change much for the top surface of the specimen. This concurrently affected by the presence of tiny air voids and the dispersion of $TiO_2$ in that these voids could easily adsorbed NOx gas with the aid of large surface area.